This repository contains an example of what the output from forcecmd looks like for a new, empty Salesforce Developer Edition org. You can use forcecmd together with a continuous integration tool and a version control system to backup and track changes to all your Salesforce organization's customizations (metadata).
Check out the travis branch for an example of how to set this up completely in the cloud using GitHub and Travis CI. In this example, Salesforce metadata is automatically downloaded on a regular schedule and committed to Git.